It has been a long felt need of builders and construction workers to have a hoist which is simple to construct, easy to use, and convenient to store. It has further been a long felt need to have a hoist which is capable of raising a heavy load, for example, an air conditioner or heavy pipe to the precise position it is to be in when installed.
Prior art attempts at providing such a hoist are represented by the following U.S. patents hereinafter discussed:
U.S. Pat. No. 3,276,546 -- Slais shows a knock-down building material elevator. However, the Slais arrangement does not allow for a heavy item to be raised to a position flush with a ceiling or roof, since the motor and drive means are located at the top of the sectional column. Further the Slais arrangement is expensive in that it includes a carriage having six rollers to facilitate movement of the hoist platform longitudinally up and down. Also the Slais arrangement is difficult to use in the sense that, in order to increase its height, one must remove a very heavy motor and drive means atop the scaffold and add an additional segment to the column and then re-attach the motor and drive means on top of the new segment. All of this would be accomplished at a very considerable height above the ground or floor as building proceeds.
Holland -- U.S. Pat. No. 3,313,376 shows a light weight elevator attachable to a scaffold. However, Holland, like Slais suffers from several disadvantages. One such disadvantage is that the motor of Holland is attached to the elevator platform adding additional weight thereto. Also the Holland arrangement requires an electrical supply cord to be attached thereto to the elevator platform and reciprocate therewith. Another disadvantage is that control of the elevator must be remote from the moving motor and drive means. And finally Holland must, by necessity, employ rollers on his platform to facilitate its movement longitudinally on the track.
One additional prior art patent which deserves mention is U.S. Pat. No. 936,911 -- Klaus et al. Klaus describes a portable hoist for putting ice into ice boxes. Klaus does not, however, provide the facility to bring his platform to a position above the upper end of his hollow mast. Thus he is not able to lift articles into a position above the top of the mast. Also, Klaus does not provide an arrangement having an inner secondary channel to provide a large load bearing surface to allow large heavy loads to be lifted, as will be discussed hereinafter with respect to the present invention. The present invention overcomes the above mentioned prior art defects and provides a straightforward inexpensive, easily constructed and readily maintained movable hoist.